This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Tubing hangers are used in completion of oil and gas wells. A typical completion system comprises a wellhead housing which is installed at the upper end of a well bore, optionally a tubing spool connected to the top of the wellhead housing including a central bore and a tubing hanger which is landed in the central bore. The process of installing a tubing hanger into a flow completion system involves positioning the tubing hanger into the tubing spool/wellhead using a tubing hanger running tool or similar device. In subsea applications, the tubing hanger is generally run through a marine riser and blowout preventer stack before landing in the tubing spool/wellhead.
The tubing hanger supports production tubing or tubing string for producing fluids from the well. The tubing string extends down into the production zone of the well and includes a production bore and defines an annulus bore surrounding the tubing string. Often, the tubing hanger provides porting to allow communication of hydraulic, electric and other downhole functions, as well as chemical injection. The tubing hanger can also serve to seal-in annulus and production areas.
For a tubing hanger installed inside a wellhead, the annulus bore which flows through the tubing hanger can be used for monitoring pressure or communicating fluid to and from the annulus below the tubing hanger. After well completion, a Christmas tree can be installed above the wellhead assembly to control production from the well. Before the Christmas tree is installed, all flow passages including the annulus bore must be sealed off to provide a temporary fluid barrier so that the blowout preventer, connected to the wellhead during completion, can be removed.
Typically, annulus isolation valves are installed inside of the tubing hanger to provide a barrier preventing annulus bore fluid communication through the tubing hanger. Traditional tubing hanger annulus isolation valves present a number of problems, including: space limitation, reliability, durability, restricted flow area, added cost and inconvenience of employing wireline tools to open and/or close the valves, and potential flow erosion of sealing surfaces. The present invention solves and/or mitigates one or more of the issues set forth above by providing a rotary disc valve capable of isolating annulus fluid communication through the tubing hanger.